It's about 15 years since I started "bleating", as one social worker described it, about adoption, though at that time I had no idea that the worst was yet to come. We had first fostered then adopted two half-sisters aged 18 months and two-and-a-half, but after initial progress the behaviour of Louise, the elder girl, was bringing the family to its knees. She and her sister, Marion, needed only tender loving care, we were told by social services. There was nothing wrong with her apart from emotional deprivation and if she was behaving strangely, it must be our fault. We persevered, putting all our energy and emotion into helping her, but by the time she was 10 we were drowning. When she was 16 she was diagnosed as psychotic.

Over the years Louise's behaviour had become too difficult for family and friends, so we were isolated in our devastation. The reaction of the social worker who had placed the two girls with us is seared into my memory: "That's hardly surprising, given the family history." The family history, it turned out, was of widespread and severe mental illness.

We then uncovered that when Louise was born there had been a case conference to decide if her mother should be allowed to take her home; she was. At 14 weeks Louise had been hit with a hammer, and further battered at 10 months. The icing on the cake: she is the result of incest between her mother and the mother's brother, so the gene pool was somewhat restricted anyway. There has been no denial that any of this was kept from us and certainly no apology, only that they had "just hoped everything would work out". We were so incensed that we wrote to the local authority asking for compensation for the other children in the family for the difficulties inflicted on them while we were trying to cope with Louise. Their response was that they were "legally covered", because by law we should have sued within three years of discovering they had withheld information from us, three years during which we were trying to cope with a mentally ill and handicapped child, and hold the rest of the family together.

Last December a couple who adopted a "wild child" who, they claimed, was so emotionally disturbed that he made their life hell, won an unprecedented claim for damages in the high court. The husband and wife, who cannot be named, claimed they would never have adopted the severely disturbed boy had they been told the true facts about him by Essex county council, which placed him and his younger sister for adoption.

Their case, the first "wrongful adoption" case to go to trial in the English courts - though several have been settled out of court - is set to reach the court of appeal in October. Its outcome is keenly awaited by a string of adoptive parents who are queueing up to sue. The Essex parents were awarded damages for the ill-effects they suffered after the boy was placed with them, but not for anything that happened post-adoption. By then, the judge ruled, they knew the worst, but went ahead regardless. (This shows a startling misunderstanding of adoption: parents are routinely told that the child will settle down, especially with the security of adoption, and all will be well once that TLC kicks in.) Both the parents and the council are appealing against the parts of the judgment that went against them.

The boy, aged five at the time of his initial placement with the couple in 1996, was later diagnosed as suffering from attention deficit hyperactivity disorder and a personality disorder. Since 1999 he has been under medication in special needs care.

In our case, the problems didn't stop with one child. Louise's musically-gifted younger sister, Marion, has always been difficult. She is malicious, has no conscience, no morality; she lies, cheats, steals and uses people, then walks away. It may be unrealistic to expect her to be the only one to escape the family tendency to mental illness, but unlike Louise she wasn't battered, and her father came from outside the family. Recently, faced with a barrage of malicious calls and letters, we had to prepare legal sanctions to stop a gifted, well-educated, well brought-up 24-year-old from harassing the only parents who ever loved her.

For Worcester teacher Helen Hale and her lecturer husband, Andrew, all of this will be familiar. They are about to become the second couple to take their local authority to court for withholding information about children placed with them.

When they discovered they could not have children, the Hales applied to adopt. A quiet, ordinary couple, they were delighted in 1987 to take half-brothers Michael, then five, and two-year-old Ben. Their alcoholic mother was in a children's home when she gave birth to Michael at 16. Three years later she had Ben by another father. By the time the Hales came on the scene she was in prison for theft and fraud.

The couple were more than prepared to lavish on the boys the tender loving care that social services told them they needed. As often happens, there was a period of progress, but when Michael became a teenager things changed. Michael had been brought up in a good home by devoted parents, had shared family holidays abroad, swum for the county and done well at school. But he was now smashing up and burgling his parents' home, shoplifting, drinking heavily and dealing in drugs. He joined the army to start afresh but was thrown out for theft and going awol. "We wouldn't see him for days," Mrs Hale told the Daily Mail - the couple are under contract to the paper and are using the money to fund their legal action - "then he'd bang on the door in the middle of the night till we let him in." In 2001 he was sentenced to 27 months in prison for burglary.

Soon Ben followed his brother's example and began taking heroin too. "It was as if he had become a different person," Mrs Hale said, recounting how he had beaten her black and blue with a telephone and held a knife at his father's throat, demanding money. The Hales tried every method of getting help from social services, only to be told that the behaviour of their sons was "normal for teenagers". Andrew Hale had a nervous breakdown and didn't work for six months.

The Hales felt like failures as parents, until they met a former Hereford and Worcester social worker who expressed surprise that the boys had remained with them. She told them that they had been been in three foster placements before the Hales had taken them, and everyone knew at the time that they would be real trouble later on. The Hales complained to social services, and an independent report said that their assessment all those years ago was that they were "a quiet couple who would be best able to cope with a child who is not expected to be permanently emotionally damaged". It also stated: "Care was clearly not taken to match the Hales with children who might fit into their lifestyle and capabilities, and the two boys, known to be ill-disciplined and grossly under-stimulated, were allowed to be adopted without any further input or advice." The most damning part of the report concluded that the Hales had been "used to the advantage of social services".

Hereford and Worcester offered the couple £3,000 compensation, which they refused. Andrew Hale says: "By not telling us the whole truth they have made our lives absolute hell, but they have also spectacularly failed two vulnerable children."

The only comment from Hereford and Worcester is: "We are unable to comment about individuals, but finding the perfect match between young children and adoptive parents is not easy. In a small number of cases it doesn't work out successfully, and we do all we can to support these families." The reality is that 20% of adoptions break down.

The child law specialist Allan Levy QC welcomes the growing number of adoptive parents who are now "bleating". He says: "The successful Essex case will give a severe jolt to adoption agencies and local authorities. It is clearly vital that parents are given all the information available."